The polyamide blocks are known to be segments that are said to be “hard” at a melting temperature (Tm) or a glass transition temperature (Tg) that is higher than the usage temperature of the polymer whereas the polyether or polyester blocks are segments to that are said to be “soft” having a Tm or Tg lower than the usage temperature of said polymer.
Document US 2004/0158027 refers to a copolyesteramide having a glass transition temperature of 0° C. or below comprising (i) at least one hard segment comprising at least one amide function and (ii) at least one soft segment comprising at least one ester function, formed from at least one fatty acid dimer and/or one fatty diol dimer. The copolymer comprises less than 15%, preferably less than 10%, advantageously less than 5% and more particularly less than 2% of ether or ether groups. According to a preferred embodiment, the copolymer does not comprise any ether groups and consists exclusively of a copolymer with hard polyamide blocks and soft polyester blocks. This copolymer is particularly useful as a hot-melt adhesive.
Document U.S. Pat. No. 5,703,177 relates to a block copolyester/polyamide comprising at least one polyester (PES) block or one copolyester (coPES) block and a polyamide or copolyamide (coPA) block enabling moulded articles to be manufactured that are biologically biodegradable and compostable, which can be used in the field of packaging, hygiene products and medical products.
Document U.S. Pat. No. 5,253,871 relates to polyetheresteramides obtained and described in FR 2,273,021. These products are copolymers formed from polyamide blocks and polyether blocks, the polyamide blocks and the polyether blocks being linked by an ester function. These products are sold under the trade name PEBAX® by Arkema. That document does not describe copolymers comprising polyester blocks.
The copolymers with polyamide blocks (abbreviated below as PA), polyether blocks (abbreviated below as PE) and polyester blocks (abbreviated below as PES) result from the copolycondensation of polyamide blocks having reactive end groups with polyether blocks and polyester blocks having reactive end groups. For example, it is possible to react:                a polyether diol, a polyester diol and a polyamide dicarboxylic acid;        a polyetherdiamine, a polyester diol and a polyamide dicarboxylic acid;        a polyetherdiamine, a polyesterdiamine and a polyamide dicarboxylic acid;        a polyether diol, a polyesterdiamine and a polyamide dicarboxylic acid;        a polyether dicarboxylic acid, a polyesterdiamine and a polyamidediamine;        a polyether dicarboxylic acid, a polyester diol and a polyamidediamine;        a polyether diol, a polyester dicarboxylic acid and a polyamidediamine; and        a polyetherdiamine, a polyester dicarboxylic acid and a polyamidediamine.        
The polyamide blocks having dicarboxylic chain ends derive, for example, from the condensation of polyamide precursors in the presence of a dicarboxylic acid chain stopper.
The polyamide blocks having diamine chain ends derive, for example, from the condensation of polyamide precursors in the presence of a diamine chain stopper.
The polymers having PA blocks, PE blocks and PES blocks may also comprise randomly distributed units. Said polymers may be prepared by the simultaneous reaction of the PE blocks, the PES blocks and the PA block precursors. Preferably, said polymers are prepared by the simultaneous reaction of the PE blocks and the PA block precursors then addition of the PES blocks in order to minimize the exchange reactions between PA blocks and PES blocks.
A polymer is obtained having mainly PE blocks, PES blocks and PA blocks of very variable length, depending on the time at which the chain stopper intervenes during the formation of the PA block, but also the various reactants which have reacted randomly and are distributed randomly along the polymer chain.
Advantageously, there are two possible types of PA blocks in the copolymers according to the invention. The polyamide block may be made up either of a “homopolyamide” structure derived from the polymerization of a single monomer namely a single lactam, a single amino acid or a single (dicarboxylic acid/diamine) pair or from a “copolyamide” type structure derived from the polymerization of a mixture of at least two monomers taken from the three aforementioned types.
The polyamide blocks are obtained in the presence of a dicarboxylic acid or a diamine chain stopper, depending on whether polyamide blocks having respectively carboxylic acid or amine ends are desired. If the precursors already comprise a dicarboxylic acid or a diamine, it is sufficient for example to use it in excess, but it is also possible to use another dicarboxylic acid or another diamine taken from the groups of dicarboxylic acids and diamines defined below.
The applicant company has now discovered that the presence of a certain quantity of PES blocks in the soft segment(s) of a copolymer having polyamide blocks and polyether blocks (abbreviated as PEBA) allows advantageous properties to be obtained in terms of low-temperature stiffening of the flexible grades, density, hydrolysis resistance (lower water uptake) and ageing (thermal oxidation and UV) resistance.